Selenium not finding button and throwing null pointer exception

Question

I'm trying to click a button using webdriver. Firepath is able to find the button using the xpath I'm giving but selenium is throwing null pointer exception. This page contains two buttons with same id and so, I tried traversing the hierarchy and found one button with a longer xpath.

Here is the HTML:

<section id="overview">
<button id="sign-me-up" class="next col-xs-10 col-xs-offset-1" ng- click="onclick($event, 'owner')">Sign Up Now</button> 

My code looks like this: I tried several things here. Three different ways to see whether the element is visible or clickable.

driver.findElement(By.xpath(//section[@id='overview']/button)).click();
driver.findElement(By.xpath(//section[@id='overview']/button[@id='sign-me-up'])).click();
driver.findElement(By.xpath(signupButton)).isDisplayed();

For any of this above, selenium is throwing null pointer exception.

I'm missing something obvious here. Please help.

Full Stack Trace:

FAILED: OnboardAnIndividualProperty
java.lang.NullPointerException
 at com.ys.page.SMBSignupLandingPage.assertIndividualOwnerPage(SMBSignupLandingPage.java:31)
 at com.ys.tests.SMB.OnboardIndividualApplicationToApprovalState.OnboardAnIndividualProperty(OnboardIndividualApplicationToApprovalState.java:34)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:84)
 at org.testng.internal.Invoker.invokeMethod(Invoker.java:714)
 at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:901)
 at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1231)
 at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
 at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
 at org.testng.TestRunner.privateRun(TestRunner.java:767)
 at org.testng.TestRunner.run(TestRunner.java:617)
 at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
 at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:329)
 at org.testng.SuiteRunner.privateRun(SuiteRunner.java:291)
 at org.testng.SuiteRunner.run(SuiteRunner.java:240)
 at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
 at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
 at org.testng.TestNG.runSuitesSequentially(TestNG.java:1224)
 at org.testng.TestNG.runSuitesLocally(TestNG.java:1149)
 at org.testng.TestNG.run(TestNG.java:1057)
 at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:111)
 at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:204)
 at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:175)

Even this throws the NullPointerException: driver.findElement(By.xpath(//section[@id='overview']

Does that mean I'm not passing the driver somewhere?

• user246: Let's go with a process of elimination. Please edit your question to specify whether this throws a NullPointException as well: driver.findElement(By.xpath("//section/[@id='overview']"))
• user246: Also, you did know specify the definition of signupButton.
• dzieciou: Can you also provide full stacktrace with NullPointerException? I'm curious because WebDriver is supposed to throw NoSuchElementException when it cannot find a matching element. I guess you may get NullPointerException because driver variable is null.
• Midha: I have added the full stack trace in the original post.
• dzieciou: Try to print driver value: System.out.println("driver=" + driver); just before exception is thrown, i.e., before line 31 of SMBSignupLandingPage class.

Answer 1

According to WebDriver API JavaDoc, if no matching elements are found then the NoSuchElementException is thrown by findElement() method, not NullPointerException. So the root cause of your problem is not a wrong XPath expression.

Instead, your stacktrace and your source code suggests this is a problem with driver variable not initialized: you try to call findElement() method on a null object.

One way to confirm that is to print the driver value:

System.out.println("driver=" + driver); 

just before the exception is thrown, i.e., before line 31 of the SMBSignupLandingPage class. Or simply run the application in debug mode, put breakpoint in same line and evaluate the value of the variable.

• Midha: Thank you dzieciou. It is because I missed to inherit the driver from the parent. Driver was null and because of that I was getting NullPointerException but once the driver was inherited, the code works.

Answer 2

yo inicialicé la variable en los metodos

(approx. translation: I would initialize the variable with a method like this)

try {
 driver = new AndroidDriver<MobileElement>(new URL("http://0.0.0.0:4723/wd/hub"), caps);
 } 
catch (MalformedURLException e) {
 }

• Kate Paulk: While your suggestion to initialize the driver variable is correct, it doesn't add anything to the accepted answer from nearly 4 years ago. I have edited your answer to format the code sample correctly, and given an approximate English translation.

Answer 3

You need to delete the class variable. If you inherit the driver from a base class, but you didn't delete the driver variable from your class. The program tries to use the class's variable instead of the super variable (it has the same name) but the class variable is not initialized, the constructor just calls to the super constructor and you get null pointer exception.